Low-temperature in-situ synthesis of cerium oxide nanoparticles applicable in EOR processes: parametric study by Taguchi approach

Abstract

In-situ synthesis of nanoparticles is a new approach to use nanoparticles in enhanced oil recovery (EOR) operations. This method synthesizes the nanomaterial under reservoir conditions and uses the reservoir's energy, which has several advantages over synthesizing these particles out of the reservoir and then injecting them into the reservoir by a dispersing fluid. Cerium oxide (CeO2) nanoparticles have very high surface energy and a very suitable catalytic property for absorbing organic substances (like crude oil) and breaking their molecules. These features can help the nanoparticles to be used in the EOR processes to recover more upgraded crude oil in heavy oil reservoirs. For the first time, this study synthesized CeO2 nanoparticles at low temperatures in crude oil as the reaction medium. Then, the Taguchi method was used to study the effects of different parameters on the size and quality of these materials. Various parameters such as pH, temperature, precursor salt concentration, and stirring time of the solution were selected to plan a design of experiment (DOE) project. Nanoparticle identification tests such as FTIR, XRD, and FESEM analyses determined nanoparticle crystalline properties, shape, morphology, and size. The results showed that high-quality CeO2 nanoparticles were produced in petroleum fluid using this study's proposed synthesis method. These nanoparticles have a spherical shape with sizes varying from 17 to 31 nm. Temperature had the most significant effect, and solution stirring time had the least impact on the crystal size of the CeO2 nanoparticles. Finally, the optimal conditions for synthesizing in-situ CeO2 nanoparticles were a combination of the temperature of 65 °C, pH of 10, the molarity of 0.55, and stirring time of 4 h.